Torque Value for Crane Slewing Gear Stud Bolts 2

[MotoGP]

Greetings and gratitude to all who are intrested in, yet another, bolt-torque plea-for-help:

Please take heart in that I have read the previous threads that pertain to bolt torque value calculations. As such, I have learned a lot about just how little I know about fasteners.

The challenge for me, obviously having precious little native ability in this area, is to understand how the maker of a Hose Handling Crane, installed on the weather deck of a SuexMax Crude Oil Carrier, arrived at: a) the clamping force for the bolts utilized in the subject application, and b) how I might arrive at a torque value based upon the information provided in the drawing.

Here goes...

One (1) slewing gear, two-part assembly (upper and lower halves), is clamped by the installation of:

A) 68 Stud Bolts, all DIN 938 Mod, M36X310 (N.B. ~ 34 of these bolts are installed on the upper half of the subject gear, and require nuts...the other half are installed in tapped holes and do not require nuts to secure them).
B) Washers, two (2) each for each of thirty-four (34) of the above bolts, and (1) each for the remaining thirty-four (34), all DIN 6916 Mod., Dia.37/66
C) One (1) Stud Nut for thirty-four (34) of the above bolts, all DIN 6915-10 Mod., M36.
D) Manufacaturer Drawing shows that each of the bolts, when installed properly (in a clockwise manner), is to apply a 610KN "clamping" force on the slewing gear halves.

It would be great to understand how the "clamping" force was derived, and subesquently the size of the fastener.

It would be AN ANSWER TO PRAYER to understand how to obtain the correct torque value from the information provided, especially that of the "lower" bolts (i.e., the bolt, with one washer, that gets threaded into the tapped hole).

Any constructive information that you could provide would meet with eternal gratitude (no kidding!).

Cheers,
Pete

To all fastener "gurus":
Please envision the question applicant bowing torso forward, and with extended arms repetitively shouting, "I'm not worthy, I'm not worthy...."

 

[CoryPad]

You didn't state explictly the property class for the studs, so I assumed property class 10.9 based upon the nuts (DIN 6915). Property class 10.9 material has a minimum ultimate tensile strength of 1040 MPa, and a minimum yield stress of 940 MPa. Typical target prestress is around 75% to 100% of yield strength, so ~ 705 to 940 MPa. An M36 x 4 externally threaded fastener has a stress area = 816.72 mm², which means the target preload should be ~ 575 to 767 kN. Apparently 610 kN was chosen as a value safely within this zone.

You can calculate the proper torque by using the method described in faq725-536. I believe the procedure during assembly should be:

Tapped hole joint
1) Fixture joint members together
2) By hand or low-output power tool, rotate stud into hole until it reaches the end of the tapped threads
3) Place washer over stud
4) By hand, rotate nut onto stud
5) Using calibrated torque method, apply torque to nut

Through hole joint
1) Fixture joint members together
2) By hand or low-output power tool, rotate stud into one of the nuts until at least one full thread extends beyond nut
3) Place washer over stud
4) Insert stud/washer/nut combination into joint
5) Place other washer over stud
6) By hand, rotate other nut onto stud
7) Using calibrated torque method, apply torque to nut, making sure other nut is not allowed to rotate

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[RockEngineer]

The US Navy NAVSHIPS TECHNICAL MANUAL 075 fasteners at

http://www.metalwebnews.org/fastners.pdf

section 075-4.5.1.2.2 gives a formula for preload. If you have access to the program PC-bolts mentioned in this document it can help you accurately calculate your torque and preload based on the materials and lubrication.

Another reference for hand calculation of preload and torque is "Mechanical Engineering Design" 5th Edition by Shigley and Mischke chapter 8-9 Bolt Preload - Static Loading.